1. Field of the Invention
This invention is directed to a ruthenium-containing catalyst system for olefin metathesis and to a catalytic olefin metathesis process employing the ruthenium-containing catalyst system.
2. Discussion of the Prior Art
Conventional ring-opening olefin metathesis polymerization (ROMP) is the catalyzed reaction of a cyclic olefin monomer to yield an unsaturated polymer: ##STR1##
Procedures to prepare polymeric hydrocarbons having reactive functional endgroups have used cyclic olefinic compounds in conjunction with a ring opening step. Ofstead, U.S. Pat. No. 3,597,403, teaches a process for ring-opening polymerization of unsaturated alicyclic compounds, preferably unsaturated alicyclic compounds of a single unsaturated alicyclic ring, in the presence of a catalyst system comprising an alkylaluminum halide, molecular oxygen, and a compound of tungsten or molybdenum; generally the single unsaturated alicyclic ring contains at least four carbon atoms and not more than five carbon atoms wherein the carbon-to-carbon double bonds in the ring are not adjacent and are non-conjugated. Streck et al., U.S. Pat. No. 3,798,175, teaches a process for ring opening polymerization of cyclic olefins and forming terminal carbalkoxy groups by employing a catalyst system consisting essentially of (1) a tungsten or molybdenum compound, (2) an organo aluminum compound, and (3) an unsaturated carboxylic acid ester. Streck et al,. U.S. Pat. No. 3,857,825, discloses a process for production of polymeric hydrocarbons having reactive silyl end groups by a ring-opening polymerization of a cyclic olefin in the presence of a catalytic amount of a halogenated compound of a metal selected from the group consisting of niobium, tantalum, molybdenum, tungsten and rhenium, and a halogen, alkoxy, carboxylate or Lewis acid.
Ruthenium-based catalysts for olefin metathesis have become of interest because they are able to effect the metathesis of certain types of olefins containing functional groups (e.g., hydroxyl, carboxylic acid, or ester groups), unlike many metathesis catalysts based on other metals such as molybdenum, tungsten, or rhenium. However, most ruthenium-based catalysts only can effect metathesis of highly strained cyclic olefins such as norbornene and norbornene derivatives, cyclobutene and cyclobutene derivatives, and dicyclopentadiene, and are unable to metathesize less strained cyclic olefins or acyclic olefins (K. J. Ivin, Olefin Metathesis, Academic Press, New York, 1983, p. 34). For example, RuCl.sub.3 catalyzes the ring-opening metathesis polymerization (ROMP) of norbornene but not olefins with significantly lower ring strain such as cyclopentene, cyclooctene, or 1,5-cyclooctadiene. L. Porri et al., Die Makromolekulare Chemie, 1974, 175: 3077-3115, reported two ruthenium compounds [dichloro(2,7-dimethylocta-2,6-diene-1,8-diyl)ruthenium and bis(trifluoroacetato)-2,7-dimethlyocta-2,6-diene-1,8-diyl)ruthenium] that are able to cause slow metathesis of cyclopentene after treatment with hydrogen, but these systems were not able to effect metathesis of cyclooctene or acyclic olefins.
More recently, A. Demonceau, et al., J. Mol. Catal., 1992, 76: 123-132; A. W. Stumpf, et al., J Chem. Soc., Chem. Commun., 1995, pages 1127-1128 and A. Demonceau, et al., Macromolecules, 1997, 30:3127-3136, reported a catalyst system which was able to effect ring opening metathesis polymerization (ROMP) of cyclooctenes. This catalyst system consists of (1) an [RuCl.sub.2 (arene)].sub.2 complex combined with a phosphine (tricyclohexyl- or triisopropyl-phosphine) and (2) an organic diazo compound such as trimethylsilyidiazomethane or ethyl diazoacetate. Also, P. Schwab et al., Angew. Chem. Int. Ed. Engl., 1995, 34: 2039-2041; P. Schwab, et al., J Am. Chem. Soc., 1996, 118: 100-110, reported a one-component ruthenium complex of the general formula RuCl.sub.2 (PR.sub.3).sub.2 (.dbd.CHR') that is able to catalyze metathesis of acyclic olefins and low-strain cyclic olefins. The catalyst reported in these two references is most active with bulky phosphine ligands such as tricyclohexyl- or triisopropyl-phospine. This one-component ruthenium complex catalyst has been prepared by several different synthetic routes, including reaction of ruthenium complexes with organic diazo compounds (P. Schwab et al., Angew. Chem. Int. Ed. Engl., 1995, 34: 2039-2041; P. Schwab, et al., J Am. Chem. Soc., 1996, 118: 100-110), with acetylene or 1-alkynes (C. Grunwald, et al., Organometallics, 1996, 15: 1960-1962; J. Wolf, et al., Angew. Chem. Int Ed., 1998, 37: 1124-1126), with propargyl and vinyl chlorides (T. E. Wilhelm, et al., Organometallics, 1997, 16: 3867-3869), and with organic dihalo compounds (T. R. Belderrain et al., Organometallics, 1997, 16: 4001-4003; M. Olivan et al., Chem. Commun., 1997, pages 1733-1734). Also, Furstner et al., Chem. Commun., 1998, pages 1315-1316, reported an effective metathesis catalyst, [Ru(.dbd.C.dbd.C.dbd.CR.sub.2)(PR.sub.3)Cl(arene)]PF.sub.6, prepared by the reaction of RuCl.sub.2 L(arene), prop-2-yn-1-ol, and NaPF.sub.6.
The catalysts reported by P. Schwab et al. and by Furstner et al. are not convenient to utilize because they are not readily available and must be synthesized in multistep procedures. Some syntheses of the catalyst of P. Schwab et al. employ organic diazo compounds such as phenyldiazomethane that are expensive, not readily available commercially, and dangerously unstable, being known to explode even at room temperature (X. Creary, Org. Synth., Coll. Vol. 7, 1990, pages 438-443). The catalyst system reported by A. Demonceau et al. and A. W. Stumpf et al. utilizes an organic diazo compound as a catalyst component.
The present invention is a ruthenium-containing catalyst for olefin metathesis that is extremely convenient to utilize because no syntheses of ruthenium complexes are required. The catalyst components are readily available from commercial sources and are utilized directly in the olefin metathesis reaction. For example, simple ruthenium chloride or bromide can be employed as the ruthenium-containing component of the catalyst. Furthermore, no organic diazo compounds are employed, and the catalysts of the present invention have high activity and selectivity for metathesis of acyclic olefins and metathesis of low-strain cyclic olefins.